An 11-year-old girl who threw a rock at a boy during a water balloon fight has escaped jail time on an assault with a deadly weapon charge as she was ordered to talk about the fight with her young victim.

Maribel Cuevas was prepared to face a felony trial on Wednesday when lawyers reached a deal that allowed her to avoid pleading guilty.

Cuevas spent five days in juvenile hall and a month under house arrest after throwing a two-pound (about one kilo) rock at 8-year-old Elijah Vang, cutting his forehead after he pelted her with a water-filled balloon.

Police, who responded with three cars while a helicopter hovered overhead, said they arrested Cuevas for resisting arrest and scratching an officer's arm.

High-ranking officials on the force defended the response, but others took up Maribel's cause, saying it was no way to treat a childish crime. Supporters gathered outside the court, chanting "Free Maribel".

As she awaited her hearing, the girl dressed in pink sweat pants, a white sweat shirt and pink flip-flops was handed a bouquet of flowers.

Maribel's father, Martin Cuevas said in Spanish after the proceeding that his daughter was not a criminal and had acted in self-defence.

"I think everything will be fine," Martin Cuevas said in Spanish.

As part of the agreement, the two children, with their parents present, will talk about what happened. Maribel will be on informal probation for six months and the charges will be dismissed if she stays in school and keeps out of trouble.